In many wartime or other hostile situations between countries or adversarial groups, anti-tank and anti-landing craft mines are deployed. These mines are typically buried on beaches and in the associated surf zones in an attempt to prevent or dissuade invasion of such a beach. These mines are encased explosive devices that are designed to detonate when disturbed, such as when a landing craft attempting to come ashore travels over one of the mines. Countermine systems have been developed to enable or assist invading forces to land on a beach where mines have been deployed. One such countermine system involves the airborne distribution of thousands of anti-mine projectiles or “darts” from a missile that is launched by an aircraft. These darts are deployed from the missile to spread across a desired area and free fall toward earth and toward the desired mine field. The darts penetrate through sand, soil, and water overburdens and upon contact with a mine are triggered, meaning the dart detonates an explosive payload.
FIG. 1 is a diagram illustrating the operation of conventional anti-mine darts 100 in detonating a deployed mine 102. The darts 100 are deployed from a missile as previously mentioned and fall towards a mine field formed by the deployed mines 102. Upon reaching the surface, the darts 100 penetrate soil, sand and/or water overburdens 104 and, once having passed through the overburdens, impact a top 106 of the mine 102. Upon impacting the top 106, the dart 100 is triggered and the timing of a payload engagement delay time Tped is initiated. The dart 100 continues to travel through TNT of the mine 102 and, upon expiration of the payload engagement delay time, the dart 100 detonates its high explosive payload. In response to the high explosive payload, the TNT and thus the mine 102 detonates, removing the threat of the mine. The payload engagement delay time Tped ensures that the dart 100 has traveled a sufficient distance into the TNT of the mine 102 such that upon detonation of the high explosive payload of the dart the TNT is detonated. If the dart 100 were to detonate upon impact of the top 106, the detonation of the high explosive payload of the dart may not detonate the TNT and thus may not cause detonation of the mine 102.
FIG. 2 is a cutaway view showing the interior of one of the conventional anti-mine darts 100 of FIG. 1 and illustrates the relatively large size of a high explosive payload 200 carried within a casing 202 of each dart. The high explosive payload 200 may be PBXN-5 or any other suitable extremely high explosive material, as will be appreciated by those skilled in the art. When PBXN-5 is used the payload is on the order of 5 grams of PBXN-5 in order to ensure proper operation of the dart. More specifically, the high explosive payload 200 must blow apart the casing 202 with sufficient energy to detonate the TNT contained in the mine 102 being detonated.
Due to the relatively large amount of the high explosive payload 200 contained within each dart 100, great care must be taken to prevent inadvertent detonation of the dart. For example, if one of the several thousand darts 100 contained within a missile detonates, the missile and possibly the plane deploying the missile could be destroyed. As a result, each dart 100 includes a safe-and-arm mechanism 300 as shown in the cross-sectional view of an individual dart in FIGS. 3A and 3B. The safe-and-arm mechanism 300 is positioned near the front of the dart 100 as illustrated in FIG. 3A while FIG. 3B is an enlarged view of the state and arm mechanism 300 showing the components in more detail. The safe-and-arm mechanism 300 includes a barrier 302 that must rotate 90° from the position shown as indicated by arrow 303 in order to establish a first condition to “arm” the dart 100 such that the high explosive payload 200 can be detonated. As each dart 100 falls after deployed from the missile, a pin 304 is forced outward as indicated by arrow 305 due to centrifugal force caused by the rotation of the dart as the dart falls to earth.
Upon initial impact with the overburdens 104 (FIG. 1), an assembly 306 of the safe-and-arm mechanism 300 shifts forward towards the front of the dart 100, as illustrated by arrow 308 in FIG. 3B to provide the second required condition for “arming” the dart. When the first and second conditions are satisfied, the barrier 302 rotates 90° from its position shown about an axis orthogonal to the cross-section of FIG. 3B. Once the barrier 302 rotates, the dart 100 is armed and ready to be detonated upon impact with a mine 102. When the front tip of the dart 100 impacts the top 106 of the mine 102, a trigger 310 ignites a primer 312 which, in turn, ignites a slow burn material 314 which provides the desired payload engagement delay time from impact of the dart with the top of the mine. The slow burn material 314 ignites an adjacent material 316 which thereafter, due to the barrier 302 having been rotated, results in ignition or detonation of the high explosive payload 200.
From this description of the operation of the safe-and-arm mechanism 300 contained within each dart 100 and the diagrams illustrated in FIGS. 2 and 3, it is seen that the safe and arm mechanism is a relatively complex structure, as is the overall structure of each dart. As a result, the manufacture of such darts 100 is relatively expensive and since thousands and possibly millions of such darts may be utilized in the types of military operations previously discussed, the manufacture and use of the darts 100 is very expensive. The safe-and-arm mechanism 300 must be utilized, however, to ensure inadvertent detonation of the high explosive payload 200 since such a detonation of one dart 100 could detonate all darts contained within a missile and such a missile could destroy the plane carrying that missile, and injure or kill the pilots and any passengers of the plane.
There is a need for an improved anti-mine dart that effectively and reliably detonates mines while having a reduced cost of manufacture and a reduced likelihood of inadvertent detonation.